Modular abrasive medium water jet cutting head

ABSTRACT

A modular abrasive agent water jet cutting head (1) has a nozzle (4) issuing a high-speed water jet (16), a mixing chamber (10) through which the high speed water jet passes (16), an abrasive agent supply line (14), and a focussing nozzle (15) forming the outlet of the mixing chamber (10). A dosing unit (12) has an axial passage of the high-speed water jet (16). The passage (18) has one or more expansions or channels (11) extending radially and which are of reduced cross section at the passage. There are preferably in each case are formed as a slits, which are only slightly wider than the diameter of the thickest abrasive particle. The expansion or channel (11) is closely connected to the passage of the high-speed water jet (16) and introduces the abrasive agent into a chordal section of the water jet (16) which is oriented in the direction of the cutting action. From there the high-speed water jet (16) receives a track of abrasive agent on its surface.

BACKGROUND OF THE INVENTION

The invention concerns a modular abrasive agent water jet cutting headwith specific abrasive agent additions.

It is known to mix an abrasive agent such as garnet or corundum into thecutting water jet in order to increase the cutting effect of the cuttingwater jet. For this the abrasive agent in a mixing chamber, throughwhich the water jet flows vertically, is fed to the water jet from theside as uniformly as possible over the entire circumference (EP 221236).

It is known that the mixing chamber can be protected with depositedabrasive agent in order to avoid erosion in the mixing chamber due tothe abrasive material, (DE-OS 384434) so that the abrasive agent iswashed specifically and directly into the water jet by injection water.In order to reinforce this, the abrasive agent is accelerated at anacute angle (DE-GM 9402916.9) and added to the mixing chamber underpressure (DE-OS 4005691).

In order to protect the focussing nozzle from the effect of the abrasiveagent, the cutting jet is surrounded with a water jacket (DE-OS4005691). For better mixing of the abrasive agent into the water jet itis known to expand the focussing nozzle in funnel-shape on the inletside (EP 110529).

According to DE-OS 3516103 a cutting jet loaded uniformly with abrasiveparticles is a condition for a clean, uniform cut. In the case ofnon-uniform distribution of the particles on one side in the mixingchamber, and thus undirected particle feed to the circumference of thepreviously described cutting heads flowing through the mixing chambercentrally, there is no uniform particle jet, as is desired. Anasymmetrically loaded mixing jet can cause a non-uniform cut and aone-sided wear of the focussing nozzle.

Precise investigations have shown that only the abrasive particleslocated on the surface in the direction of cut of the mixed jet producea cutting effect. The abrasive particles located in the interior or onthe sides of the jet turned away from the direction of cutting do notproduce a cutting effect.

The purpose and task of the invention is to apply abrasive particles onthe surface of the cutting jet, in the respective direction of cuttingthus in order to increase the cutting power with a reduction of the useof the abrasive agent.

SUMMARY OF THE INVENTION

The knowledge that only the abrasive particles located on the surface ofthe cutting jet in the direction of cutting are effective leads to theapparatus of the present invention in which the mixing chamber known upto now has inserted thereinto a dosing unit. Extending axiallytherethrough is an opening for the passage of the cutting jet Alaterally extending channel extends radially outwardly therefrom to theabrasive agent supply line. Abrasive particles are introduced into achordal portion to the surface of the cutting jet to concentrate theabrasive particles in a chordal sector 30° to 60° wide from this channelwith a ratio of the diameter of the abrasive particles to that of thecutting beam of approximately 1:4. By turning the cutting head or thedosing unit around the axis of the cutting beam, controlledcorresponding to the cutting parameters, the sector loaded with abrasiveagent emerges from the focussing nozzle on the side of the cutting beamwhich is in the direction of cutting. By means of using a dosing unitwith several expansions for delivering the abrasive particlesdistributed uniformly around the cutting beam, of which only theexpansion(s) located approximately in the cutting direction is (are)charged with abrasive particles, it is possible to reduce the angle ofrotation for the cutting head, or mount the cutting head in a fixedposition. In the modular abrasive agent water jet cutting head there isan adjusting element, with which these parts can be adjustedindividually and/or completely for securing the alignment of thejet-guiding elements and thus for assuring a collimation of thejet-forming head components.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is to be explained in greater detail below by means of anembodiment. The respective drawing shows in FIG. 1 a longitudinalsection through a modular cutting head in principle,

FIG. 2 a dosing unit in the longitudinal section,

FIG. 3 a dosing unit in cross-section.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

A modular cutting head 1 is connected to a collimation pipe 2 with ahigh-pressure connection 3. There is a nozzle orifice 4 in front of theend of the collimator pipe 2. A central channel 6 passes through theentire modular cutting head 1 along the middle axis thereof, startingfrom the nozzle orifice 4. The modular cutting head 1 is enclosed by ahousing 7, which is closed with a focussing nozzle holder 8. The modularcutting head 1 is held with screws 9.

In the interior of the housing 7 there is a mixing chamber 10, whichcontains a dosing unit 12 provided with an axial passage 18 for the jet,a radially extending expansion or channel 11. The dosing unit 12 ispositioned in the mixing chamber 10 with a spacer 13. An abrasive agentsupply line 14 opens laterally into the mixing chamber 10. The channel11 is located in front of the abrasive agent supply line 14. A focussingnozzle 15 held by the focussing nozzle holder 8 is connected in theaxial direction of the modular cutting head 1. A high-speed water jet 16generated by the nozzle orifice 4 flows through the modular cutting head1 in the central channel 6 in the axial direction along the middle axis5. A stream of abrasive agent is introduced to a chordal section of thecross section of the high-speed water jet. For this there is a passage18 in the middle of the dosing unit 12, which is fixed by means of agroove 17. The hole 18 has a diameter corresponding approximately to thediameter of the high-speed water jet 16. The wall of the passage 18 isbisected by the channel 11. The abrasive agent is applied only to thechordal section of the high-speed water jet 16 located in front of theexpansion 11. The modular cutting head 1 is turned during cutting sothat at the outlet of the focussing nozzle 15, the water set sector withthe abrasive agent always emerges on the side of the high-speed waterjet 16 located in the direction of cutting.

Having thus described the invention, what is claimed is:
 1. In a modularabrasive agent water jet cutting head (1) having a nozzle (4) forissuing a high-speed water jet (16), a mixing chamber (10) through whichthe high-speed water jet (16) passes, an abrasive agent supply line (14)and a focussing nozzle (15) forming the outlet of the mixing chamber(10), the improvement comprising; a dosing unit (12) in the mixingchamber (10) and having an axial passage (18) for the high-speed waterjet (16) to pass therethrough, said dosing unit (12) having a lateralchannel (11) extending radially from said axial passage for thehigh-speed water jet (16) to said abrasive agent supply line and throughwhich a stream of abrasive agent from said supply line (14) may beintroduced, said radial passage narrowing in cross section from saidsupply line to said axial passage to introduce the abrasive agent into achordal portion of the high-speed water jet (16) located in the cuttingdirection.
 2. The modular abrasive agent water jet cutting head (1) inaccordance with claim 1,.wherein said lateral channel (11) narrows to aslit at said axial passage which is only slightly wider than thediameter of the thickest particle of abrasive agent to be fedtherethrough.
 3. The modular abrasive agent water jet cutting head (1)in accordance with claim 1, wherein said cutting head (1) is rotatableabout the axis of the high-speed water jet (16).
 4. The modular abrasiveagent water jet cutting head (1) in accordance with claim 1, whereinsaid dosing unit (12) is rotatable around the axis of the high-speedwater jet (16).
 5. The modular abrasive agent water jet cutting head (1)in accordance with claim 1, wherein said dosing unit (12) has an axialguide groove (17) in its periphery to orient said lateral channel insaid cutting head.